#include "G711Codec.h"

#include <stdio.h>

#define         SIGN_BIT        (0x80)      /* Sign bit for a A-law byte. */
#define         QUANT_MASK      (0xf)       /* Quantization field mask. */
#define         NSEGS           (8)         /* Number of A-law segments. */
#define         SEG_SHIFT       (4)         /* Left shift for segment number. */
#define         SEG_MASK        (0x70)      /* Segment field mask. */
#define         BIAS            (0x84)      /* Bias for linear code. */
#define		CLIP            8159


#define		DATA_LEN	(16)

static short seg_aend[8] = {
	0x1F, 0x3F, 0x7F, 0xFF,
	0x1FF, 0x3FF, 0x7FF, 0xFFF
};

static short seg_uend[8] = {
	0x3F, 0x7F, 0xFF, 0x1FF,
	0x3FF, 0x7FF, 0xFFF, 0x1FFF
};

static unsigned char _u2a[128] = {
	/* u- to A-law conversions */
	1,1,2,2,3,3,4,4,
	5,5,6,6,7,7,8,8,
	9,10,11,12,13,14,15,16,
	17,18,19,20,21,22,23,24,
	25,27,29,31,33,34,35,36,
	37,38,39,40,41,42,43,44,
	46,48,49,50,51,52,53,54,
	55,56,57,58,59,60,61,62,
	64,65,66,67,68,69,70,71,
	72,73,74,75,76,77,78,79,
	81,82,83,84,85,86,87,88,
	89,90,91,92,93,94,95,96,
	97,98,99,100,101,102,103,104,
	105,106,107,108,109,110,111,112,
	113,114,115,116,117,118,119,120,
	121,122,123,124,125,126,127,128
};

static unsigned char _a2u[128] = {
	/* A- to u-law conversions */
	1,3,5,7,9,11,13,15,
	16,17,18,19,20,21,22,23,
	24,25,26,27,28,29,30,31,
	32,32,33,33,34,34,35,35,
	36,37,38,39,40,41,42,43,
	44,45,46,47,48,48,49,49,
	50,51,52,53,54,55,56,57,
	58,59,60,61,62,63,64,64,
	65,66,67,68,69,70,71,72,
	73,74,75,76,77,78,79,79,
	80,81,82,83,84,85,86,87,
	88,89,90,91,92,93,94,95,
	96,97,98,99,100,101,102,103,
	104,105,106,107,108,109,110,111,
	112,113,114,115,116,117,118,119,
	120,121,122,123,124,125,126,127
};

static short search(int val, short *table, int size)
{
	int i;
	for (i = 0; i < size; i++) {
		if (val <= *table++)
			return (i);

	}
	return (size);
}

/*
* linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
*
* linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
*
*Linear Input CodeCompressed Code
*---------------------------------------
*0000000wxyza000wxyz
*0000001wxyza001wxyz
*000001wxyzab010wxyz
*00001wxyzabc011wxyz
*0001wxyzabcd100wxyz
*001wxyzabcde101wxyz
*01wxyzabcdef110wxyz
*1wxyzabcdefg111wxyz
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/
unsigned char linear2alaw(int pcm_val)/* 2's complement (16-bit range) */
{

	int mask;
	int seg;
	unsigned char aval;

	pcm_val = pcm_val >> 3;

	if (pcm_val >= 0) {
		mask = 0xD5;/* sign (7th) bit = 1 */
	}
	else {
		mask = 0x55;/* sign bit = 0 */
		pcm_val = -pcm_val - 1;
	}

	/* Convert the scaled magnitude to segment number. */
	seg = search(pcm_val, seg_aend, 8);

	/* Combine the sign, segment, and quantization bits. */

	if (seg >= 8)/* out of range, return maximum value. */
		return (unsigned char)(0x7F ^ mask);
	else {
		aval = (unsigned char)seg << SEG_SHIFT;
		if (seg < 2)
			aval |= (pcm_val >> 1) & QUANT_MASK;
		else
			aval |= (pcm_val >> seg) & QUANT_MASK;
		return (aval ^ mask);
	}

}

/*
* alaw2linear() - Convert an A-law value to 16-bit linear PCM
*
*/
int alaw2linear(unsigned char a_val)
{

	int t;
	int seg;

	a_val ^= 0x55;

	t = (a_val & QUANT_MASK) << 4;
	seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
	switch (seg) {
	case 0:
		t += 8;
		break;
	case 1:
		t += 0x108;
		break;
	default:
		t += 0x108;
		t <<= seg - 1;

	}
	return ((a_val & SIGN_BIT) ? t : -t);
}


/*
* linear2ulaw() - Convert a linear PCM value to u-law
*
* In order to simplify the encoding process, the original linear magnitude
* is biased by adding 33 which shifts the encoding range from (0 - 8158) to
* (33 - 8191). The result can be seen in the following encoding table:
*
*Biased Linear Input CodeCompressed Code
*---------------------------------------
*00000001wxyza000wxyz
*0000001wxyzab001wxyz
*000001wxyzabc010wxyz
*00001wxyzabcd011wxyz
*0001wxyzabcde100wxyz
*001wxyzabcdef101wxyz
*01wxyzabcdefg110wxyz
*1wxyzabcdefgh111wxyz
*
* Each biased linear code has a leading 1 which identifies the segment
* number. The value of the segment number is equal to 7 minus the number
* of leading 0's. The quantization interval is directly available as the
* four bits wxyz.  * The trailing bits (a - h) are ignored.
*
* Ordinarily the complement of the resulting code word is used for
* transmission, and so the code word is complemented before it is returned.
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/
unsigned char linear2ulaw(short pcm_val)/* 2's complement (16-bit range) */
{
	short mask;
	short seg;
	unsigned char uval;

	/* Get the sign and the magnitude of the value. */
	pcm_val = pcm_val >> 2;
	if (pcm_val < 0) {
		pcm_val = -pcm_val;
		mask = 0x7F;
	}
	else {
		mask = 0xFF;
	}
	if (pcm_val > CLIP)
		pcm_val = CLIP;/* clip the magnitude */
	pcm_val += (BIAS >> 2);

	/* Convert the scaled magnitude to segment number. */
	seg = search(pcm_val, seg_uend, 8);

	/*
	* Combine the sign, segment, quantization bits;
	* and complement the code word.
	*/
	if (seg >= 8)/* out of range, return maximum value. */
		return (unsigned char)(0x7F ^ mask);
	else {

		uval = (unsigned char)(seg << 4) | ((pcm_val >> (seg + 1)) & 0xF);
		return (uval ^ mask);
	}
}

/*
* ulaw2linear() - Convert a u-law value to 16-bit linear PCM
*
* First, a biased linear code is derived from the code word. An unbiased
* output can then be obtained by subtracting 33 from the biased code.
*
* Note that this function expects to be passed the complement of the
* original code word. This is in keeping with ISDN conventions.
*/
short ulaw2linear(unsigned char u_val)
{
	short t;

	/* Complement to obtain normal u-law value. */
	u_val = ~u_val;

	/*
	* Extract and bias the quantization bits. Then
	* shift up by the segment number and subtract out the bias.
	*/
	t = ((u_val & QUANT_MASK) << 3) + BIAS;
	t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
	return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
}

/* A-law to u-law conversion */
unsigned char alaw2ulaw(unsigned char aval)
{
	aval &= 0xff;
	return (unsigned char)((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :
		(0x7F ^ _a2u[aval ^ 0x55]));
}

/* u-law to A-law conversion */
unsigned char ulaw2alaw(unsigned char uval)
{
	uval &= 0xff;
	return (unsigned char)((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :
		(unsigned char)(0x55 ^ (_u2a[0x7F ^ uval] - 1)));
}

int encode(char *a_psrc, char *a_pdst, int in_data_len, unsigned char type)
{

	int i;
	short *psrc = (short *)a_psrc;
	int out_data_len = in_data_len / sizeof(short);

	if (a_psrc == NULL || a_pdst == NULL) {
		return (-1);
	}

	if (in_data_len <= 0) {
		return (-1);
	}


	if (type == G711_A_LAW) {
		for (i = 0; i < out_data_len; i++) {
			a_pdst[i] = (char)linear2alaw(psrc[i]);
		}
	}
	else {
		for (i = 0; i < out_data_len; i++) {
			a_pdst[i] = (char)linear2ulaw(psrc[i]);
		}
	}
	return (i);
}

int decode(char *a_psrc, char *a_pdst, int in_data_len, unsigned char type)
{

	int i;
	short *pdst = (short *)a_pdst;
	int out_data_len = in_data_len / sizeof(char);

	if (a_psrc == NULL || a_pdst == NULL) {
		return (-1);
	}

	if (type == G711_A_LAW) {
		for (i = 0; i < out_data_len; i++) {
			pdst[i] = (short)alaw2linear((unsigned char)a_psrc[i]);
		}
	}
	else {
		for (i = 0; i < out_data_len; i++) {
			pdst[i] = (short)ulaw2linear((unsigned char)a_psrc[i]);
		}
	}

	return (i * sizeof(short));
}





